The present claimed invention relates to the field of flat panel displays. More particularly, the present claimed invention relates to the formation of a row electrode for a flat panel display screen structure.
Field emission display devices are typically comprised of numerous layers. The layers are formed or deposited using various fabrication process steps. Prior Art FIG. 1A is a schematic side sectional view of a portion of a pristine conventional field emission display structure. More specifically, Prior Art FIG. 1A illustrates an emitter electrode layer 100 having an overlying resistive layer 102 and an overlying inter-metal dielectric layer 104. Field emitter structures, typically shown as 106a and 106b, are shown disposed within cavities formed into inter-metal dielectric layer 104. A gate electrode 108 is shown disposed above inter-metal dielectric layer 104. As mentioned above, Prior Art FIG. 1 schematically illustrates a portion of a pristine conventional field emission display structure. However, conventional field emission display structures are typically not pristine. That is, manufacturing and fabrication process variations often result in the formation of a field emission display structure containing significant defects.
With reference next to Prior Art FIG. 1B, a side sectional view of a portion of a defect-containing field emission display structure is shown. During the fabrication of conventional field emission display structures, the aforementioned layers are often subjected to caustic or otherwise deleterious substances. Specifically, during the fabrication of various overlying layers, emitter electrode layer 100 is often subjected to processes which adversely affect the integrity of emitter electrode 100. As shown in the embodiment of Prior Art FIG. 1B, certain fabrication process steps can deleteriously etch or corrode emitter electrode 100. In fact, some conventional fabrication processes can result in the complete removal of at least portions of emitter electrode 100. Such degradation of emitter electrode 100 can render the field emission display device defective and even inoperative.
With reference next to Prior Art FIG. 1C, a side sectional view of a portion of another defect containing field emission display structure is shown. In addition to unwanted corrosion or etching of the emitter electrode, other defects can occur which degrade or render the field emission display structure inoperable. In the embodiment of Prior Art FIG. 1C, feature 110 represents a xe2x80x9cshortxe2x80x9d extending between emitter electrode 100 and gate electrode 108. Such shorting can occur in a conventional field emission display device when the emitter electrode is not properly insulated from the gate electrode. That is, if a region on the conductive surface of the emitter electrode is exposed and, therefore, not properly insulated from the gate electrode, shorting to the gate electrode can occur. Portions of the emitter electrode may remain exposed when deposition of various layers over the emitter electrode is not consistent or complete, or when the layers are degraded (e.g. etched or corroded) by subsequent process steps. The inconsistent deposition or degradation of the layers between the emitter electrode and the gate electrode can result in the existence of non-insulative paths which extend from the emitter electrode to the gate electrode. Such a short can render the field emission display device defective and even inoperative. All of the above-described defects result in decreased field emission display device reliability and yield.
Referring now to Prior Art FIG. 1D, a simplified schematic top plan view of emitter electrode and gate electrode orientation is shown. As shown in Prior Art FIG. 1D, emitter electrodes 150, 152, 154, and 156 are typically the display row electrodes and are conventionally disposed underlying gate electrodes 158, 160, and 162 which are typically display column electrodes. Only a few emitter and column electrodes are shown in Prior Art FIG. 1D for purposes of clarity. It will be understood, however, that in a conventional field emission display device numerous additional emitter and column electrodes will be present.
Referring still to Prior Art FIG. 1D, during typical operation, one of row electrodes 150, 152, 154, and 156 will have a current driven therethrough. A desired one of column electrodes 158, 160, and 162 has an electrical potential applied with respect to the row electrodes such that the subpixel located at the intersection of the activated column and emitter electrode emits electrons. It will be understood that in conventional field emission display devices each subpixel has a corresponding intersection of an emitter and a column. For example, when emitter electrode 150 has current passed therethrough and column electrode 158 has a potential applied thereto, the subpixel corresponding to the intersection of emitter electrode 150 and column electrode 158 will emit electrons. Additionally, in conventional field emission display devices, subpixels are oriented in rows across the display. Therefore, when current is passed through a row electrode each and every subpixel in that row is activated (the subpixel emits electrons only when the corresponding column electrode has the said electrical potential applied thereto). Thus, the current in the row electrode must supply all the subpixels in that row. For purposes of the present discussion it will be assumed that the current is driven through row electrodes 150, 152, 154, and 156 by drivers 164, 166, 168, and 170, respectively. That is, in the representation of Prior Art FIG. 1D, the current is passed through row electrodes 150, 152, 154, and 156 from left to right. As a result of activating each and every subpixel in the row (i.e. sharing the row electrode current between all of the subpixels), a subpixel corresponding to, for example, the intersection of row electrode 150 and column 158 will be more brightly illuminated than the subpixel corresponding to, for example, the intersection of row electrode 150 and column 160 due to the voltage drop along the row caused by the emitter current drain from each activated subpixel. This decrease or xe2x80x9cdrop-offxe2x80x9d in the brightness of subpixels adversely affects the characteristics of a field emission display device.
Furthermore, the emitter electrodes must also be protected from degradation during subsequent processing. The emitter electrodes must also be manufactured and utilized in a manner which reduces shorts occurring between the emitter electrode and the gate electrode.
Thus, a need exists for a field emission display device wherein display characteristics such as display brightness are not degraded by current drain across the length of the row electrode. Still another a need exists for a field emission display structure which is less susceptible to emitter electrode degradation. A further need exists for a gate electrode structure and gate electrode formation method for use in a field emission display device wherein the gate electrode reduces the occurrence of gate to emitter shorts.
The present invention provides a field emission display device wherein display characteristics such as display brightness are not degraded by current drain across the length of the row electrode. The present invention further provides a field emission display structure which is less susceptible to emitter electrode degradation. The present invention also provides a gate electrode structure and gate electrode formation method for use in a field emission display device wherein the gate electrode reduces the occurrence of gate to emitter shorts.
Specifically, in one embodiment, the present invention provides a structure and method for forming a column (sometimes referred to as xe2x80x9crowxe2x80x9d) electrode for a field emission display device wherein the column (or row) electrode is disposed beneath the field emitters and the row (or column) electrode. In one embodiment, the present invention comprises depositing a resistor layer over portions of a column (or row) electrode. Next, an inter-metal dielectric layer is deposited over the column (or row) electrode. In the present embodiment, the inter-metal dielectric layer is deposited over portions of the resistor layer and over pad areas of the column (or row) electrode. After the deposition of the inter-metal dielectric layer, the column (or row) electrode is subjected to an anodization process such that exposed regions of the column (or row) electrode are anodized. In so doing, the present invention provides a column (or row) electrode structure which is resistant to gate to emitter shorts and which is protected from subsequent processing steps.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.